Mode localization in plasmonic optomechanical resonators for ultrasensitive infrared sensing.

Uncooled infrared thermal detectors are gaining increasing attention owing to their ability to operate at room-temperature and their low cost. This study proposes a plasmonic optomechanical resonator for ultrasensitive long-wave infrared wave sensing based on mode localization mechanism. The mode-localized effect confines the plasmonic energy in the resonators and induces a significant modal amplitude shift through infrared irradiation, thus achieving highly sensitive detection. The results show that the detection sensitivity can reach 1.304 /mW, which is three-order improvement compared to the frequency-shift sensing metrics. The research provides a new approach to further improve the detection sensitivity of uncooled infrared sensors.

Research Progress on Intrinsically Conductive Polymers and Conductive Polymer-Based Composites for Electromagnetic Shielding.

Electromagnetic shielding materials are special materials that can effectively absorb and shield electromagnetic waves and protect electronic devices and electronic circuits from interference and damage by electromagnetic radiation. This paper presents the research progress of intrinsically conductive polymer materials and conductive polymer-based composites for electromagnetic shielding as well as an introduction to lightweight polymer composites with multicomponent systems. These materials have excellent electromagnetic interference shielding properties and have the advantages of electromagnetic wave absorption and higher electromagnetic shielding effectiveness compared with conventional electromagnetic shielding materials, but these materials still have their own shortcomings. Finally, the paper also discusses the future opportunities and challenges of intrinsically conductive polymers and composites containing a conductive polymer matrix for electromagnetic shielding applications.

Graphene-Based Metamaterial Sensor for Pesticide Trace Detection.

Organophosphate insecticides with broad spectrum and high efficiency make a great difference to agricultural production. The correct utilization and residue of pesticides have always been important issues of concern, and residual pesticides can accumulate and pass through the environment and food cycle, resulting in safety and health hazards to humans and animals. In particular, current detection methods are often characterized by complex operations or low sensitivity. Fortunately, using monolayer graphene as the sensing interface, the designed graphene-based metamaterial biosensor working in the 0-1 THz frequency range can achieve highly sensitive detection characterized by spectral amplitude changes. Meanwhile, the proposed biosensor has the advantages of easy operation, low cost, and quick detection. Taking phosalone as an example, its molecules can move the Fermi level of graphene with π-π stacking, and the lowest concentration of detection in this experiment is 0.01 µg/mL. This metamaterial biosensor has great potential in detecting trace pesticides, and its application in food hygiene and medicine can provide better detection services.

Effect of Electrospinning Network Instead of Polymer Network on the Properties of PDLCs.

In this study, polymer-dispersed liquid crystal (PDLC) membranes were prepared by combining prepolymer, liquid crystal, and nanofiber mesh membranes under UV irradiation. EM, POM, and electro-optic curves were then used to examine the modified polymer network structure and the electro-optical properties of these samples. As a result, the PDLCs with a specific amount of reticular nanofiber films had considerably improved electro-optical characteristics and antiaging capabilities. The advancement of PDLC incorporated with reticulated nanofiber films, which exhibited a faster response time and superior electro-optical properties, would greatly enhance the technological application prospects of PDLC-based smart windows, displays, power storage, and flexible gadgets.

Fluorescent Dye-Doped Brightening Polymer-Stabilized Bistable Cholesteric Liquid Crystal Films.

Brightening polymer-stabilized bistable cholesteric liquid crystal (PSBCLC) films with doped fluorescent dyes were prepared using the polymerization-induced phase separation (PIPS) method. The transmittance performance behavior of these films in both states (focal conic and planar) and absorbance change in multiple dye concentrations were studied using a UV/VIS/NIR spectrophotometer. The change occurring in dye dispersion morphology with different concentrations was obtained by means of the polarizing optical microscope. The maximum fluorescence intensity of different dye-doped PSBCLC films was measured using a fluorescence spectrophotometer. Moreover, the contrast ratios and driving voltages of these films were calculated and recorded to demonstrate film performance. Finally, the optimal concentration of dye-doped PSBCLC films with a high contrast ratio and a relatively low drive voltage was found. This is expected to have great potential applications in cholesteric liquid crystal reflective displays.

Slot hybrid-core waveguides for temperature-independent integrated optical sensors.

We propose a novel type of waveguides, called the slot hybrid-core waveguides (HCWs), for temperature-independent integrated optical sensors. The HCWs are composed of different core materials having the opposite thermo-optic coefficients (TOCs) and, therefore, are immune to temperature variations. On this basis, slot HCWs are proposed for the microring resonator-based optical sensors, enabling the sensors to simultaneously present high sensitivities and temperature independence. The temperature-dependent wavelength shifts of the proposed sensors are calculated to be less than 1 pm/K while the sensitivities to the cladding refractive indices attain 468 nm/RIU and 536 nm/RIU, respectively, for the asymmetric and symmetric slot structures.

Sensors for simultaneous measurement of temperature and humidity based on all-dielectric metamaterials.

In this study, a new type of sensors based on all-dielectric metamaterials that can measure temperature and relative humidity simultaneously was designed and theoretically analyzed in detail. The proposed metamaterial sensor consists of a quartz substrate in the bottom layer, polydimethylsiloxane (PDMS) in the middle layer, and a periodic silicon structure on the top layer. CST Studio Suite was used to determine the transmission spectrum of the metamaterials in the near-infrared band using finite integration, and two transmission dips were observed. Then, polyvinyl alcohol (PVA) was used as the humidity-sensitive material to be coated on the surface of this metamaterial sensor, and these two transmission dips were used to measure the temperature and relative humidity simultaneously. Simulation results showed that the sensitivities of the two dips to the temperature are -0.224 and -0.069 nm/°C, and the sensitivities to the relative humidity are -0.618 and -0.521 nm/%, respectively. Based on the sensitivity matrix, the temperature and the relative humidity can be measured simultaneously. The proposed sensor has the advantages of polarization insensitivity, small size and low loss, which makes it have many application potentials in various research fields, including physics, biology and chemical sensing.

Smallholder Farmers Contribution to Food Production in Nigeria.

Several studies have shown that smallholder farmers produce most of the food in low-income and developing countries and form the backbone of the country's food supply. This study examines the extent these smallholder farmers in Nigeria can put the country on the path to self-sufficiency and ensure satiety for household food consumption through their local production. The study also examines food production and their resulting yield based on crop production and harvested area, as well as the percentage of crops produced for food or other purposes. The results show that production of rice, sorghum, soybean, cassava, and yam is low; and their corresponding yields are declining, with the exception of maize, although the harvested area increased from 2015 to 2018. As it is, the findings are a clear indication of inadequate per capita food supply due to low food production, especially for cereals. The study suggests closing the yield gap specifically for cereals, limiting post-harvest losses, and finding a sustainable balance between the uses of major food crops for animal feed to reduce pressure on land resource use. The different states production performance requires special attention to harness the agricultural potential of each geopolitical zone. Lastly, dry-season cultivation should be encouraged through irrigation to enable harvesting two-times in a year. The study offers useful approaches to assess the contribution of local farmers to the food supply of a growing population and provides suggestions for the government, stakeholders, and the international community willing to collaborate and invest in the agricultural sector.

Cold Chain Food and COVID-19 Transmission Risk: From the Perspective of Consumption and Trade.

Since the outbreak of the coronavirus disease 2019 (COVID-19), political and academic circles have focused significant attention on stopping the chain of COVID-19 transmission. In particular outbreaks related to cold chain food (CCF) have been reported, and there remains a possibility that CCF can be a carrier. Based on CCF consumption and trade matrix data, here, the "source" of COVID-19 transmission through CCF was analyzed using a complex network analysis method, informing the construction of a risk assessment model reflecting internal and external transmission dynamics. The model included the COVID-19 risk index, CCF consumption level, urbanization level, CCF trade quantity, and others. The risk level of COVID-19 transmission by CCF and the dominant risk types were analyzed at national and global scales as well as at the community level. The results were as follows. (1) The global CCF trade network is typically dominated by six core countries in six main communities, such as Indonesia, Argentina, Ukraine, Netherlands, and the USA. These locations are one of the highest sources of risk for COVID-19 transmission. (2) The risk of COVID-19 transmission by CCF in specific trade communities is higher than the global average, with the Netherlands-Germany community being at the highest level. There are eight European countries (i.e., Netherlands, Germany, Belgium, France, Spain, Britain, Italy, and Poland) and three American countries (namely the USA, Mexico, and Brazil) facing a very high level of COVID-19 transmission risk by CCF. (3) Of the countries, 62% are dominated by internal diffusion and 23% by external input risk. The countries with high comprehensive transmission risk mainly experience risks from external inputs. This study provides methods for tracing the source of virus transmission and provides a policy reference for preventing the chain of COVID-19 transmission by CCF and maintaining the security of the global food supply chain.

Flexible graphene-based metamaterial sensor for highly sensitive detection of bovine serum albumin.

A graphene-based metamaterial sensor working in the terahertz spectrum is proposed, simulated, and experimentally verified by measuring bovine serum albumin (BSA). Flexible, low-cost polyimide (PI) is used as the substrate, and aluminum with periodic square rings is chosen as the metal layer. Furthermore, the introduction of the graphene monolayer interacts with the molecules through π-π stacking, resulting in the highly sensitive detection of BSA by calculating the amplitude changes at the resonance frequency. The sensor, which is a biosensor platform that offers the advantages of a small size, high sensitivity, and easy fabrication, is a promising method for THz biological detection.

Broadband terahertz metamaterial absorber: design and fabrication.

We proposed and experimentally demonstrated a broadband terahertz (THz) metamaterial absorber based on a symmetrical L-shaped metallic resonator. The absorber structure produces two absorption peaks at 0.491 and 0.73 THz, with the absorption rates of 98.6% and 99.6%, respectively. Broadband absorption was obtained from 0.457 to 1 THz, achieving a >90% absorption bandwidth of 0.543 THz. By analyzing the distributions of the electric and magnetic field at the two resonance frequencies, electric and magnetic dipole resonances were proposed to explain the broadband absorption mechanism. Furthermore, various widths and lengths of the symmetrical L-shaped metallic resonator on the absorption characteristics were investigated. Moreover, the broadband absorption characteristic can be maintained with an incident angle of up to 45° for transverse-electric and 30° for transverse-magnetic polarization. Finally, we experimentally observed a >70% broadband absorption characteristic from 0.42 to 1 THz. This proposed absorber has the potential for bolometric imaging, modulating, and spectroscopy in the THz region.

Optical Fiber Based Mach-Zehnder Interferometer for APES Detection.

A 3-aminopropyl-triethoxysilane (APES) fiber-optic sensor based on a Mach-Zehnder interferometer (MZI) was demonstrated. The MZI was constructed with a core-offset fusion single mode fiber (SMF) structure with a length of 3.0 cm. As APES gradually attaches to the MZI, the external environment of the MZI changes, which in turn causes change in the MZI's interference. That is the reason why we can obtain the relationships between the APES amount and resonance dip wavelength by measuring the transmission variations of the resonant dip wavelength of the MZI. The optimized amount of 1% APES for 3.0 cm MZI biosensors was 3 mL, whereas the optimized amount of 2% APES was 1.5 mL.

Risk of Global External Cereals Supply under the Background of the COVID-19 Pandemic: Based on the Perspective of Trade Network.

International food trade is an integral part of the food system, and the COVID-19 pandemic has exposed the fragility of external food supplies. Based on the perspective of cereals trade networks (CTN), the pandemic risk is combined with the trade intensity between countries, and an assessment model of cereals external supply risk is constructed that includes external dependence index (EDI), import concentration, and risk of COVID-19 from import countries index (RICI). The results show that: (1) the global main CTN have typical scale-free characteristics, and seven communities are detected under the influence of the core countries; (2) about 60%, 50%, and 70% of countries face risks of medium and above (high and very high) external dependence, concentration of imports, and COVID-19 in the country of origin, respectively. Under the influence of the pandemic, the risk of global external cereal supply index (RECSI) has increased by 65%, and the USA-CAN communities show the highest risk index; (3) the countries with a very high risk are mainly the Pacific island countries and the Latin American and African countries. In addition, Japan, Mexico, South Korea, and 80% of the net food-importing developing countries are at high or very high RECSI levels. Approximately 50% of countries belong to the compound risk type, and many export countries belong to the RICI risk type; (4) global external food supply is subjected to multiple potential threats such as trade interruption, "price crisis", and "payment dilemma". The geographical proximity of community members and the geographical proximity of the pandemic risk is superimposed, increasing the regional risk of external food supply; and (5) this study confirms that the food-exporting countries should avoid the adoption of food export restriction measures and can prevent potential external supply risks from the dimensions of maintaining global food liquidity and promoting diversification of import sources. We believe that our assessment model of cereals external supply risk comprises a useful method for investigations regarding the international CTN or global food crisis under the background of the pandemic.

Prodrug-based nano-delivery strategy to improve the antitumor ability of carboplatin in vivo and in vitro.

Chemotherapy plays a major role in the treatment of cancer, but it still has great limitations in anti-tumor effect. Carboplatin (CAR) is the first-line drug in the treatment of non-small cell lung cancer, but the therapeutic effect is demonstrated weak. Therefore, we modified CAR with hexadecyl chain and polyethylene glycol, so as to realize its liposolubility and PEGylation. The synthesized amphiphilic CAR prodrugs could self-assemble into polymer micelles in water with an average particle size about 11.8 nm and low critical micelles concentration (0.0538 mg·mL-1). In vivo pharmacodynamics and cytotoxicity experiment evidenced that the polymer micelles were equipped with preferable anti-tumor effect, finally attained the aim of elevating anti-tumor effect and prolonging retention time in vivo. The self-assembled micelles skillfully solve the shortcomings of weak efficacy of CAR, which provides a powerful platform for the application of chemical drug in oncology.

All-metal terahertz metamaterial biosensor for protein detection.

In this paper, a terahertz (THz) biosensor based on all-metal metamaterial is theoretically investigated and experimentally verified. This THz metamaterial biosensor uses stainless steel materials that are manufactured via laser-drilling technology. The simulation results show that the maximum refractive index sensitivity and the figure of merit of this metamaterial sensor are 294.95 GHz/RIU and 4.03, respectively. Then, bovine serum albumin was chosen as the detection substance to assess this biosensor's effectiveness. The experiment results show that the detection sensitivity is 72.81 GHz/(ng/mm2) and the limit of detection is 0.035 mg/mL. This THz metamaterial biosensor is simple, cost-effective, easy to fabricate, and has great potential in various biosensing applications.

High sensitivity temperature sensor based on a side-hole fiber.

This paper proposes a temperature sensor based on a side-hole fiber (SHF). The sensor is formed by single-mode fiber (SMF)-coreless fiber (CLF)-SHF-CLF-SMF fusion splicing. The SHF adopts the dislocation fusion splicing method to ensure that one air hole is exposed. Two different interferences form a superposition, making the response more sensitive. The experiment shows that the sensitivity during heating and cooling is 1.587 nm/°C and 1.681 nm/°C, respectively, in the temperature range of 25-45°C. The sensor has high temperature sensitivity, exhibits easy processing, is smaller in size, and has important research value for temperature monitoring in daily life and industrial production.

Design and Fabrication of a Triple-Band Terahertz Metamaterial Absorber.

We presented and manufactured a triple-band terahertz (THz) metamaterial absorber with three concentric square ring metallic resonators, a polyethylene terephthalate (PET) layer, and a metallic substrate. The simulation results demonstrate that the absorptivity of 99.5%, 86.4%, and 98.4% can be achieved at resonant frequency of 0.337, 0.496, and 0.718 THz, respectively. The experimental results show three distinct absorption peaks at 0.366, 0.512, and 0.751 THz, which is mostly agreement with the simulation. We analyzed the absorption mechanism from the distribution of electric and magnetic fields. The sensitivity of the three peaks of this triple-band absorber to the surrounding is 72, 103.5, 139.5 GHz/RIU, respectively. In addition, the absorber is polarization insensitive because of the symmetric configuration. The absorber can simultaneously exhibit high absorption effect at incident angles up to 60° for transverse electric (TE) polarization and 70° for transverse magnetic (TM) polarization. This presented terahertz metamaterial absorber with a triple-band absorption and easy fabrication can find important applications in biological sensing, THz imaging, filter and optical communication.

Beta-elemene inhibits differentiated thyroid carcinoma metastasis by reducing cellular proliferation, metabolism and invasion ability.

BACKGROUND: Accelerated glycolysis is a characteristic of carcinoma. The herb-derived compound, beta (ß)-elemene, has shown promising anticancer effects against various tumors by inhibiting aerobic glycolysis. However, its activity against thyroid carcinoma and the mechanism is still unknown. METHODS: Differentiated thyroid carcinoma (DTC) cell lines, including papillary thyroid carcinoma (PTC) cell lines (IHH-4, TPC-1, K1), and follicular thyroid carcinoma (FTC) cell line (FTC133) were treated with different concentration of ß-elemene. The viability of DTC cells was analyzed using the CCK8 method. Cell cycle and apoptosis analysis were performed by flow cytometry and western blotting. The cell invasion ability was evaluated in Transwell assays. Energy metabolism in living cells was measured using a Seahorse XF analyzer. The antitumor effects of ß-elemene were analyzed in vivo in a nude mouse xenograft tumors model. RESULTS: CCK8 assays showed ß-elemene significantly inhibited DTC cell proliferation in a dose- and time-dependent manner. ß-elemene promoted cell apoptosis, with increased expression of cleaved caspase-9 and decreased BCL-2 expression. Transwell assays showed that ß-elemene significantly inhibited the invasion ability of DTC cells. ß-elemene also reduced angiogenesis by decreasing VEGF expression in DTC cells. ß-elemene reduces the basal oxygen consumption rate (OCR), extracellular acidification rate (ECAR), and maximal glycolytic capacity as well as maximal respiration and ATP production. Moreover, ß-elemene inhibited tumor growth in a mouse xenograft model in vivo. CONCLUSIONS: In this study, we have provided the first evidence of the antitumor effects of ß-elemene, which was shown to inhibit cell proliferation, promote apoptosis, induce cell cycle arrest, inhibit cell invasion ability and reduce angiogenesis. Furthermore, we showed that ß-elemene significantly inhibits the respiratory and glycolytic ability of human DTC cells. Thus, our findings show the potential of ß-elemene as a novel treatment for DTC.

Tunable broadband all-silicon terahertz absorber based on a simple metamaterial structure.

We propose and demonstrate a modulatable all-silicon terahertz absorber based on a cylindrical metamaterial structure. Broadband absorption is obtained from 0.86 to 2.00 THz, with an average absorbance of 94%, indicating a wide absorption bandwidth of 1.14 THz. The maximum absorption, around 1.24 THz, is up to 98%. We employ simulation results to investigate the physical properties of the absorption, and we attribute the broadband absorption to a combination of electric dipole and magnetic dipole modes. Furthermore, the tunable response of the all-silicon terahertz absorber under the optical pump beam, with different fluences, is studied using a hierarchical model for simulating the carrier density of the gradient distribution. Moreover, different polarizations and oblique incidences of terahertz waves are used to verify the polarization and angle-of-incidence insensitivity of the device. The absorber provides a simple method to design a modulated broadband terahertz absorber, and the design scheme is scalable to develop various tunable broadband absorbers at other frequencies. This work holds great potential in modulator applications, imaging devices, and energy conversion.

Microfluidic flow direction and rate vector sensor based on a partially gold-coated TFBG.

In microfluidic chips applications, the monitoring of the rate and the direction of a microfluidic flow is very important. Here, we demonstrate a liquid flow rate and a direction sensor using a partially gold-coated tilted fiber Bragg grating (TFBG) as the sensing element. Wavelength shifts and amplitude changes of the TFBG transmission resonances in the near infrared reveal the direction of the liquid flowing along the fiber axis in the vicinity of the TFBG due to a nanoscale gold layer over part of the TFBG. For a device length of 10 mm (and a diameter of 125 µm for easy insertion into microfluidic channels), the flow rates and the direction can be detectable unequivocally. The TFBG waveguiding properties allow such devices to function in liquids with refractive indices ranging from 1.33 to about 1.40. In addition, the proposed sensor can be made inherently temperature-insensitive by referencing all wavelengths to the wavelength of the core mode resonance of the grating, which is isolated from the fiber surroundings.